Overview: Paul Murton discovers the source of the River Nith, high in a remote forestry plantation. Heading downstream, he hears the story of the Knockshinnoch mining disaster - how 116 men were saved from entombment after a massive earth collapse. He also learns about the first man to make a bicycle with pedals, heads to the riverside home of Robbie Burns and finds out how a Dumfries man helped Neil Armstrong walk on the moon.